Actual split

OK, all instances of item group "chemistry" now broken into:
chemschool: emphasis on Safety, textbooks, negligible chance for
mutagen/purifier :-/
chemhome: more Ingredients, marginally better odds of good stuff
chem-Lab: the Labs now spawn mutagen recipes.

Also split off the Lab dorms from the generic Bedroom spawns.  Much more
caffeine, electronics, and Lab gear, less kidlit.  Hope that's OK.
Reference fix

In order to get the new item groups to work, needed to change the
references here.  Looked straightforward.
Drop update

Destroying the old "chemistry" category also meant changing over the
zombie-scientist drops.
Missed a close-bracket

Thanks for the checker, AtomicDryad.
Syntax fixes

OK, underscored everything and I think the indentation was a problem
with Notepad++ using tabs to keep the newlines aligned.  (Looks the same
on this end, at least without manually taking the cursor down the list
and watching for jumps.  Sorry.)

Converted it all to spaces; hope that works.
Merge branch 'pr/4474'
Minor formatting fixes.